US Secretary of State Rex Tillerson made a pit stop in Bangkok on Tuesday with a plea to the kingdom to curb business ties with North Korea, as Washington rounds up allies for its bid to halt Pyongyang’s nuclear ambitions.

Tillerson is the highest level American diplomat to visit Thailand since a 2014 coup strained ties between the long-time friends and saw China court Bangkok with massive arms sales and infrastructure deals.

Thailand is one of several Southeast Asian countries to host a North Korean embassy and enjoys valuable bilateral trade with the reclusive regime.

In 2014 the two countries shared trade worth $126 million, according to Thailand’s Ministry of Foreign Affairs, a near three-fold increase since 2009.

But America wants Thailand to crack down on North Korean firms that use the capital as a trading hub through front businesses, according to acting US Assistant Secretary of State for East Asian Affairs Susan Thornton.

Tillerson will also lean on the kingdom to tighten visa requirements for North Koreans entering Thailand and squeeze its diplomatic mission, Thornton added.

Thai junta chief Prayuth Chan-ocha beamed as he welcomed the US envoy to Government House.

After their meeting a Thai government spokesman said the kingdom was ready to “co-operate and give its support” to solve the crisis on the Korean peninsula, adding the kingdom “is complying with” beefed-up UN sanctions targeting Pyongyang.

Those sanctions could cost North Korea $1 billion a year.

Tillerson’s one-day visit follows a regional forum in Manila, where the former ExxonMobil CEO hailed the new sanctions regime on North Korea over its growing nuclear arsenal.

They were levied - with the agreement of North Korean lifeline China - in response to the launch of two intercontinental ballistic missile tests last month.

The US is also urging Thailand to take in more North Korean refugees, Thornton said ahead of the visit.

The kingdom has long been a transit route for defectors who make the arduous journey through China, then into Laos or Cambodia and Thailand, where they seek sanctuary at the South Korean Embassy. But it does not officially recognise them as refugees.

Analysts say Thailand is unlikely to significantly redraw its North Korean ties.

The kingdom has a history of “tiptoeing (between) various states that have problems,” Thitinan Pongsudhirak, a foreign policy expert at Chulalongkorn University, said.

Tillerson told US embassy staff he wanted to “grow” the relationship between America and its oldest Asian ally, “even in its ups and downs”.

It was not immediately clear how firmly the former oilman would push the junta government on its crackdown on political rights.

Watch: ‘North Korea halting tests best signal for talks’

US President Donald Trump’s administration re-set ties with Thailand after relations hit the buffers following the 2014 coup.

The US condemned the army takeover and edged away from the regime, trimming back military aid.

But Trump, who has enraged rights groups by cosying up to strongmen around the globe, has reached out to the junta chief directly and extended a White House invite.

The thaw also comes amid Washington’s growing concerns over rival superpower China’s clout in the region.

Beijing entices its smaller neighbours by offering massive investment decoupled from human rights concerns, which appeals to leaders weary of US pressure.

Thailand is a lynchpin country in China’s massive trade and infrastructure “One Belt, One Road” strategy.

China wants to build a high-speed railway through Thailand to its southern ports.